Editor's note: For a full investigation into the Anoka-Hennepin student suicides, watch "CNN Presents" on Saturday, July 30, at 8 p.m. ET.

(CNN) -- Federal authorities are investigating "incidents involving harassment and bullying" in Minnesota's largest school district, the U.S. Department of Justice confirmed in an e-mail to CNN.

The civil rights investigation is under way in the suburban Minneapolis school district, Anoka-Hennepin, a community already embattled in a culture war over homosexuality in the classroom.

The Justice Department together with the Department of Education's Office of Civil Rights are looking into "allegations of harassment and discrimination in the Anoka-Hennepin School District based on sex, including peer-on-peer harassment based on not conforming to gender stereotypes," according to a district memo provided exclusively to CNN.

The district said the joint investigation included interviews with staff members by federal authorities.

Proud to be 'Born This Way'

"The Department is committed to investigating allegations to determine whether there are violations of federal civil rights laws and will use the enforcement tools at our disposal to protect the safety of students," wrote a Justice Department spokeswoman in an e-mail to CNN.

The federal investigation comes after a string of seven student suicides in less than two years, which stirred public debate over the district's sexual orientation curriculum policy.

Parents and friends say four of those students were either gay, perceived to be gay or questioning their sexuality, and they say, at least two of them were bullied over their sexuality.

It's unclear whether the suicides or the policy are a significant part of the federal investigation. The controversial policy, adopted in 2009, states that staff must "remain neutral on matters regarding sexual orientation" and that "such matters are best addressed within individual family homes, churches or community organizations."

Anoka-Hennepin is the only Minnesota school district known to have such a policy. However, at least eight other states -- Alabama, Arizona, Louisiana, Mississippi, Oklahoma, South Carolina, Texas and Utah -- have statutes specifying varying limits on classroom instruction regarding homosexuality. Tennessee considered similar legislation this year.

Community supporters of the so-called neutrality policy say it is constitutional and consistent with the Minnesota Human Rights Act, which protects rights based on sexual orientation but states that nothing in the law shall be construed to "authorize or permit the promotion of homosexuality or bisexuality in education institutions."

Gay rights advocates who oppose Anoka-Hennepin's neutrality policy say the school district has misinterpreted the intention of the state's human rights law.

15-year-old Justin Aaberg committed suicide last July. His mother Tammy says he was bullied because he was gay.

In May, two advocacy groups, the Southern Poverty Law Center and the National Center for Lesbian Rights, threatened the school district with a federal lawsuit challenging the policy. So far, negotiations with the school district have not met their demands.

The head of the Anoka-Hennepin school district said the policy reflects a community divided over homosexuality.

"It's a diverse community," said Anoka-Hennepin Superintendent Dennis Carlson, "and what we're trying to do, what I'm trying to do as a superintendent, is walk down the middle of the road."

Tammy Aaberg -- whose 15-year-old son, Justin, committed suicide last July -- has become an outspoken critic of the neutrality policy.

"He came to me and said, 'Mom, a kid at school says I'm going to go to hell because I'm gay,'" said Aaberg.

The neutrality policy, she said, contributed to a school environment harmful to her son, who was outed in the eighth grade by another student.

"I believe that the climate that they have in the school, the way that kids are allowed to treat other kids -- they say 'fag' all the time," Aaberg said. "If you're even questioning who you are and you're not seeing anybody who's like you, you don't see anything positive about who you are, then you start wondering, 'What's wrong with me?'"

The district -- which has a separate and comprehensive bullying prohibition policy -- has continually denied any connection between bullying and the suicides.

"It's really difficult to say that with any suicide, this instance or that instance caused a suicide," Carlson said. "We have no evidence that bullying or harassment took place in any of those cases."

"It's a diverse community, and ... what I'm trying to do as a superintendent is walk down the middle of the road.
--Anoka-Hennepin Superintendent Dennis Carlson

The superintendent also emphasized the importance of students reporting bullying, and he acknowledged, "Gay students in our district struggle with bullying and harassment on a daily basis."

Sam Wolfe, the Southern Poverty Law Center attorney handling the advocacy group's case, calls the curriculum policy a "gag policy." In May, Wolfe wrote a letter to Carlson stating that students who are lesbian, gay, bisexual and transgender and those perceived to be LGBT "remain in jeopardy in a hostile and alienating environment."

"The gag policy singles out LGBT students by denying them and them alone any affirmation of their identity," Wolfe wrote in the May 24 letter.

He also said the policy "categorically preclud(es) any meaningful classroom discussion about history, literature, current events or any other relevant lessons involving LGBT people."

The district's letter also disputes that the policy prohibits classroom discussion of LGBT issues, but states rather that it prevents teachers from injecting their personal beliefs on homosexuality into the classroom.

Some teachers in Anoka-Hennepin school district say the neutrality policy is difficult to implement.

"Neutrality is tricky to understand," said Julie Blaha, the president of Anoka-Hennepin's teachers' union. "We have to clarify -- is neutrality silence? Is neutrality balance? Is neutrality purely factual? Is neutrality showing both sides?

"When people say they like neutrality I think what they're saying is they like the idea of fairness," Blaha said, "And I think we all agree with that, the idea that everyone feels safe, everyone feels welcome in our classrooms; however, when you look at the policy, I'm not sure that's what the policy is saying. And that's the problem, we're not sure what exactly this policy says."

This week the district asked the advocacy groups to help them develop employee training to support LGBT students but stopped short of meeting their demands to repeal the neutrality policy.

"We believe the interests of our students would be better served if we could put our energies and resources into working together to develop materials that directly support students," said Carlson. "Rather than focusing on litigation we would prefer to invest in materials that would provide a positive outcome for students for years to come."

The district also announced it retained counsel to look into the bullying allegations of other students brought to light by the advocacy groups. The outside law firm's investigation, the district said, found its response "prompt, reasonable and appropriate in each case."

Carlson said the school board has no plan to change the neutrality policy.

"It is disappointing that the Anoka-Hennepin School District continues to be in denial that it has a serious problem," said Wolfe in a press release, announcing a press conference for Thursday morning.

The Department of Justice did not comment on whether its investigation will determine if the policy is compliant with federal law.

A similar federal investigation in Tehachapi, California, led to federally mandated revisions of the Tehachapi Unified School District's policies.

After investigating a complaint surrounding the suicide of a 13-year-old student, the departments of Justice and Education concluded the eighth grader "suffered sexual and gender-based harassment by his peers, including harassment based on his nonconformity to gender stereotypes" and the school district "did not adequately investigate or respond appropriately as it is required to do by federal law," according to the resolution agreement reached this month between the Tehachapi Unified School District and the federal agencies.

Tehachapi district officials disagreed with the investigation's findings.